This invention relates to display signs wherein an array of electromagnetically actuated disks selectively flip between a bright side of the disk being in view and an opposite dark side of the disk being in view.
In the past, electronic flip disk or flip dot signs have been produced having an array of these disks mounted in a housing. The disks are magnetic and electromagnets are used to flip or rotate the disks, so that alternate bright or ON sides are in view or opposite dark or OFF sides are in view. Preselected disks are chosen to have their bright or ON sides displayed in a particular pattern, such as alphanumeric characters or a graphic image.
In the prior art displays, the electromagnetic actuating devices are usually in the form of poles with coils wound thereon. The wires that form the windings of these coils need to be connected to a power source, and this usually done by providing terminal posts or connector pins to which the ends of the wires are electrically connected. An example of this is shown in U.S. Pat. No. 4,577,427 issued to John Browne.
A difficulty with these prior art flip disk displays, however, is that the size of the flip disks cannot be made small enough. The size of the flip disks is related to the spacing between the electromagnetic coils that actuate the disks and the connector pins that electrically connect the wires of the coils. In the manufacturing process for making these devices, the poles of the electromagnets and the connector pins are first mounted in a base or housing member on which the flip disks are mounted. The coils are then wound on the poles and the connector pins by automated winding machines. There is a limit as to how close together the poles and connector pins can be placed, or the winding machines cannot get in to wind the coils. As a result, flip disk signs in the past have been limited to where the disks have a width or diameter that cannot be made much less than about 0.9 centimeters. For a high resolution display sign, the disks need to be much smaller than that and spaced much more closely together.
The present invention provides a means and method for eliminating the connector pins in an electromagnetic display sign, so that the electromagnet poles can be spaced very close together and consequently the flip disks can be made very small, yet the coils on the electromagnet poles can still be wound using conventional coil winding apparatus.
According to one aspect of the invention, there is provided a flip dot display element comprising a housing and a disk-like member pivotally mounted in the housing to rotate about a pivot axis between an ON position showing a bright surface on one side of the disk-like member and an OFF position showing a dark surface on the opposite side thereof. The disk-like member includes a magnet having a magnetic axis transverse to the pivot axis. A pair of opposed spaced-apart poles are mounted in the housing on either side of the pivot axis and extend below the disk-like member to pole lower distal end portions. The poles include first coils wound thereon in series to produce reversible magnetic fields in the poles of opposite polarity to interact with the disk-like member magnet and flip the disk-like member between the ON and OFF positions. The poles include second coils located on the respective pole lower distal end portions and connected in series with the respective first coils. Also, a conductive coating is formed on the second coils in electrical contact therewith, the conductive coatings forming electrical contacts for energizing the first coils.
According to another aspect of the invention, there is provided a method of making a flip dot display formed of display elements having magnetic disk-like members pivotally mounted in a housing. The method comprises the steps of mounting spaced-apart poles in the housing extending below each disk-like member to flip the disk-like members upon magnetic fields being induced in the poles. First insulated wire coils are wound onto the coils in series to induce reversible magnetic fields of opposite polarity in the poles. Second insulated wire coils are wound on the poles in series respective with the first coils and located below the first coils. The second coils are then dipped into molten solder to remove the wire insulation therefrom and form electrical contacts for energizing the first coils.